1,721,120 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Different sensitivities of p42 mitogen-activated protein kinase to phorbol ester and okadaic acid tumor promoters among cell types
No full textThe operational equivalence of different types of tumor promoters was studied by comparing immediate, early, and late effects of okadaic acid (OA) and 12-O-tetradecanoylphorbol-13-acetate (TPA) on the phosphorylation state of p42 mitogen activated protein kinase isoform (ERK2) in eight different cell lines. In normal human and mouse fibroblasts, both agents stimulated immediate/early (15-60 min) phosphorylation of ERK2. In mouse 3T3 cells, enhanced phosphorylation of ERK2 was detected only within the first hour of treatment with TPA but not with OA. The early response to both TPA and OA, in rum, was lost in another established cell line, the PNT2 prostate epithelial cells, where we could detect increased levels of phosphorylated ERK2 only after a 24-hr treatment with OA. When the effect of OA was evaluated in different PNT cell strains, we observed that their capacity to respond to this agent, by stabilizing phosphorylated forms of ERK2, was lost in less differentiated strains. In HeLa S-3 and HTC tumor cells, however, neither TPA nor OA treatment led to any detectable increase in ERK2 phosphorylation at any time point analyzed. We conclude that the effects of OA and TPA on the phosphorylation states of ERK2 could be related to the cell type, and that the operational equivalence between these two different tumor promoters is maximal in normal cells
Proanthocyanidins from Vitis vinifera inhibit oxidative stress-induced vascular impairment in pulmonary arteries from diabetic rats
Full text linkBackground Vitis vinifera L. (grape seed extract) is a natural source of proanthocyanidins with antioxidant and free radical-scavenging activities. Hypothesis Grape seed extract supplementation may prevent vascular endothelium impairment associated with diabetes mellitus in rat pulmonary artery. Study design We evaluated endothelial function of rat pulmonary artery ex-vivo at the intermediate stage (4 weeks) of streptozotocin (STZ)-induced diabetes mellitus. We also evaluated the protective effect of grape seed extract administered daily, beginning the day after diabetes induction, or 15 days after diabetes induction, until the day of sacrifice. In addition, we compared the effect of grape seed extract supplementation with that of vitamin C. Methods Rats were made diabetic with streptozotocin (STZ, 65 mg/kg i.v.). Thirty days later rats were sacrificed and pulmonary vessels reactivity and endothelial function compared to that of age-matched healthy animals. Results Concentration-response curves to ACh, NE, sodium nitroprusside (NO donor), but not to histamine and iloprost (prostacyclin analog), were significantly altered 4 weeks after STZ-injection. Antioxidant supplementation (3 mg/kg/day) with either vitamin C or grape seed extract, starting the day after diabetes induction, significantly improved vasodilation to ACh and SNP. Norepinephrine-induced contractions were preserved by grape seed extract, but not vitamin C supplementation. Conversely, vitamin C but not grape seed extract showed beneficial effects contrasting the loss of body weight in diabetic animals. Abnormal vascular function was not reversed when antioxidant supplementations were postponed 15 days after the induction of diabetes. Conclusions This study provides scientific support for the therapeutic potential of an antioxidant therapy in endothelial impairment associated with diabetes. A daily supplementation of grape seed proanthocyanidins and/or vitamin C given at the earlier stage of disease may have a complementary role in the pharmacological therapy of diabetes and pulmonary vascular dysfunction
A possible role for urinary bladder epithelium in bradykinin-induced contraction in diabetic rats
No full textDiabetes provokes a greater responsiveness of rat urinary bladder preparations to bradykinin and a greater formation and release of prostaglandin F2 alpha, without affecting prostaglandin E2 release significantly. Inhibition of cyclooxygenase by indomethacin (1 microM) inhibits the contraction elicited by bradykinin and leads to identical contractile responses of control and diabetic urinary bladder strips. Removal of the urinary bladder epithelium does not modify the contractile response evoked by bradykinin in control preparations but significantly decreases the contraction of preparations of diabetic tissues. Quantitatively, the activity of control urinary bladder strips with epithelium and the activity of diabetic preparations without epithelium are the same. More prostaglandin F2 alpha is released into the medium by urinary bladder strips devoid of epithelium in both control and in diabetic rats. These results indicate a role for epithelial cells in the smooth muscle contraction evoked by bradykini
Altered neurogenic and mechanical responses to acetylcholine, ATP and substance P in detrusor from rat with outlet obstruction
No full textThe well-known side effects of anticholinergic compounds used to treat urinary incontinence caused by detrusor overactivity have addressed the interest on other pharmacological intervention. The purpose of the present work was to investigate the possible changes in purinergic and cholinergic components of parasympathetic neurotransmission in obstructed rat bladders with detrusor overactivity, and to examine the effect of the association of suramin, atropine and indomethacin on nerve-mediated responses to electrical field stimulation (EFS). Mechanical responses to exogenous acetylcholine, ATP and substance P were also evaluated. Altered sensitivities to acetylcholine and to the sensory neurotransmitter substance P, but unchanged sensitivity to the stable ATP analogue alpha,beta-methyleneATP were observed in bladders from obstructed rats. Suramin and atropine inhibited purinergic and cholinergic components of the neurogenic responses evoked by EFS in detrusor strips from control and obstructed rats. Interestingly, suramin enhanced the antagonistic effect of atropine on neurogenic responses of detrusor strips at all frequencies of stimulation tested. Our results suggest that the association between an antimuscarinic drug and an antagonist of P2X purinoceptors such as suramin might be helpful to reduce the therapeutic dosage of the antimuscarinic drug, along with its side effects. This approach may be of interest in the therapy of patients with bladder incontinence caused by detrusor overactivity, which do not even respond to a maximal dosage of antimuscarinic dru
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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